1. Field of the Invention
This invention relates to the conversion of coal to electricity via conventional power generation equipment, such as direct fired or steam turbines, or other known types of generator sets. It more particularly refers to an efficient means of maximizing electricity output to meet demand while minimizing capital outlay.
2. Description of the Prior Art
Coal has been used for many years as boiler fuel. For a long time it was the most significant energy source in the electricity generating industry. With the advent of cheap petroleum and natural gas, the use of coal diminished and with increasingly stringent ecological standards being required, the use of coal has shrunk to become a relatively minor factor in the electric power generation industry. Now that natural gas and petroleum are in short supply and have become more expensive, there has been an increasing resurgence in consideration of coal for electric power generation. Two major problems, other than cost, still exist however; the ecological unacceptability of the high sulfur emissions, and the fact that coal, as a solid, is more difficult to handle than the hydrocarbon fluids.
Thus, there has also been an increase in consideration being given to convert coal into a fluid form, via gasification to a mixture comprising carbon monoxide and hydrogen, i.e., synthesis gas, or via hydrogenative liquifaction to a heavy syn-crude type of product. Both of these fluids are relatively easily desulfurized and can be handled very nicely. Coal liquifaction is relatively expensive because it requires the addition of hydrogen from outside sources, such as water, which are not always readily, inexpensively available in proximity to the coal fields. Gasification has generally used oxygen, which is fairly expensive, but readily available anywhere by means of air liquifaction and fractionation.
Electricity generation is a highly capital sensitive industry. Since the generating companies are public utilities, they have an obligation to meet the public's demands for electricity at all times. These demands are by no means uniform or even. In fact, peak loads may be as high as three (3) time base loads. These public utilities must have sufficient generating equipment to meet these peak loads. One way to handle this problem is to have multiple parallel facilities and to run as many of them as needed to supply the power required. This is practical and in fact is the way many electric utilities operate. Using a gaseous fuel feed however requires that reserves of the fuel be kept on hand to meet peak load demand. This has made it necessary to use pressurized fuel storage facilities, in order to conserve space, with the attendant hazards and costs thereof.
If one considers the use of coal, in the form of synthesis gas, for fuel to fire electric power generators, the gaseous fuel storage problem is aggravated by the fact that synthesis gas has a higher volume per BTU than does natural gas or LPG; and if one seeks to avoid the capital requirements of installing an oxygen plant, to support the coal gasification, and therefore desires to use air, the problems of pressurized fuel storage increase by orders of magnitude because of the nitrogen dilution factor.
It is, therefore, an important object of this invention to provide a novel means of converting coal to electricity taking into account the load disparity between base demands and peak demands.
It is another object of this invention to provide a novel means of converting coal to electricity through an intermediate mixture of combustible liquid and gas.
It is still another object of this invention to convert coal to electricity by utilizing air gasification of coal, rather than the more costly oxygen gasification of coal.
Other and additional objects will become apparent from a consideration of this entire specification including the drawing and the claims hereof.